Location: Plant, Soil and Nutrition ResearchTitle: AtPDS over-expression in tomato: exposing unique patterns of carotenoid self-regulation and an alternative strategy for the enhancement of fruit carotenoid content
|Mcquinn, Ryan - Cornell University - New York|
|Wong, Briana - Cornell University - New York|
Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2017
Publication Date: 7/13/2017
Citation: Mcquinn, R., Wong, B., Giovannoni, J.J. 2017. AtPDS over-expression in tomato: exposing unique patterns of carotenoid self-regulation and an alternative strategy for the enhancement of fruit carotenoid content. Plant Biotechnology Journal. doi:10.1111/pbi12789.
Interpretive Summary: Carotenoids (e.g. lutein, b-carotene and lycopene) and their catabolites (i.e. vitamin A and others) are integral in the human diet as they ensure proper development and aid in the prevention of numerous age-related diseases. Humans’ inability to synthesize carotenoids de novo makes them dependent on plants as their primary source of dietary carotenoids, the acquisition of which is dependent upon both content in specific plant tissues and their ability to be absorbed in the digestive tract (bioavailability). The capacity of many fruits to accumulate elevated levels of carotenoids as they ripen makes fruits an important source of dietary carotenoids in many diets. Here, we (i) identify the carotenoid enzyme PDS as a useful target for manipulation towards carotenoid enhancement in ripening tomato fruit, (ii) fully characterize the effect of PDS overexpression on carotenoid content and carotenoid gene expression in fruit and other plant organs and (iii) demonstrate the utility of PDS overexpression combined with alteration of other enzymes as a means to both elevate carotenoid levels and modify carotenoid accumulation profiles towards more bioavailable forms that will positively impact human health and nutrition.
Technical Abstract: The regulation of plant carotenogenesis is an active research area for both biological discovery and practical implementation. In tomato, we demonstrate additional bottlenecks exist in the poly-cis-transformation of phytoene to lycopene in the context of ripening-induced PSY1 expression and activity and reveal phytoene desaturase (PDS), as a target for manipulation towards elevated lycopene content in maturing tomato fruit. Overexpression of Arabidopsis PDS, AtPDS, elevated PDS transcript abundance in all aerial tissues resulting in both altered carotenoid accumulation and associated pathway gene expression in a tissue-specific manner. Significant increases in downstream carotenoids (all-trans-lycopene and b-carotene) and minimal changes in carotenogenic gene expression (carotenoid isomerase-like 1, CRTIL1) suggest overexpression of heterologous AtPDS in tomato circumvents endogenous regulatory mechanism observed with previous strategies. AtPDS overexpression in the background of the tangerine (carotenoid isomerase, CRTISO) mutant exposes its potential in elevating downstream cis- lycopene accumulation in ripe tomato fruit, as cis-lycopene is more bioavailable yet less abundant than all-trans-lycopene in the wild-type control. In summary, we demonstrate the limitation of PDS in ripening fruit, its utility in modifying carotenoid profiles towards improved quality, and reveal novel carotenoid pathway feedback regulation.